Electric ship propulsion



Jan. 29 1924. 1,481,882

E. F. w. ALEXANDERSON I ELECTRIC SHIP PROPULSION Filed Feb. 16. 1920 10 Sheets-Sheet 1 Fly.

4 IO a Ernst FW. Alexanderson,

" His Attorney.

Jan. 29, 1924.

' E. F. ALEXANDERSON ELECTRIC SHI P PROPULS I 0N Filed Feb. 16, 1920 10 Sheets-Sheet 2 w W rz 9 m M m 7 e. WM s O 0 I e f: Mm L Z a LT 4145MB a a w f 53 flUCC N o no 0000 N 00000 m0 9 00000 80 0 00000 N D R m L m f E S H H A R r. E H in: v smzfls L NAPWL /l o L UFR REU F BPHF Inventor: Ernst FW. Alexanderson,

* by His Attorney.

Jan. 29, 1924. 1,481,882

E. F. w. ALEXANDERSON ELECTRIC SHIP PROPULSION Filed Feb. 16. 1920 10 Sheets-Shoot 5 V 789IOIIZ8273031 22 ruu. $5550 41/540 0 o o o OPE/V TRANS/"fl? o o 0 #500050 a ERA/(MIG o o o o 0 0500050 191 TRANSFER o o o o o 0 0500050 //V01/CT/0N o o o 0 0500050 sr/vcwnozv/zms. o o o 0 05011050 TRANS/5R o o o o 0 05011650 #500050 c0550 0 o o 0 05011050 51/54 55550 A8759 0 o o 0 055111 In ventor.

Ernst FW. Alexanderson,

His Attorney.

Jan. 29 1924.

E. F. w. ALEXANDERSON ELECTRIC SHI P PROPULS ION Filed Feb. 16. 1920 10 Sheets-Sheet L Fig.4.

- mu SPEED Rial/CED SPEED REDUCED SP0 I FULL SPEED Inventor Ernst F. W. Alexanderson,

His Attorney.

Jan. 29, 1924. 1,481,882

E. F. W. ALEXANDERSON ELECTRIC SHIP. PROPULSION Filed Feb. 16. 1920 10 Sheets-Shoot 5 Inventor". ErnestFw. Alexanderson 9 M Q M wvx L 953E A Q55: 01 H W M Q His Attorneg.

Jan. 29, 1924.

E. F. w. ALEXANDERSON ELECTRIC SHIP PROPULS ION File'd Feb. .16 1920 10 Sheets-Sheet 6 Inventor:

Ernst F W. Alexanderson,

HIS Attorney.

Fig. 7.

Jan. 29, 1924. 1,481,882 E. F. w. ALEXANDERSON ELECTRIC SH IP PROPULS I ON Filed .Feb. 16. 1920 10 Sheets-Shoot 7 vi m 5 I: [2 7 U3 0 s b k m o DELA YED OPENlNG inventor: ErnestFTWAiexanderson,

q 0 I WM His Attorney.

Jan. 29, 1924. 1,481,882

. E. F. w. ALEXANDERSON ELECTRIC SHIP PROPULSION 10 Sheets-Sheet 8 Filed Feb. 16. 1920 Inventor Ernst F. W. Alex ariderson,

by MW His Attorney.

Jan. 29 1924. 1,481,882

E. F. W. ALEXANDERSON ELECTRIC SHIP PROPULSION 1O Sheets-Shoot 9 Filed Feb. 16. 1920 J as v r if Inventor:

H'is Attorneg Ernst FW Alexandersovw Jan. 29 1924.

' 1,481,882 E. F. W. ALEXANDERSON ELECTRIC SHIP PROPULSION Filed Feb. 16, 1920 10 Sheets-Sheet 10 Inventor:

Ernst. F. W. A l exanchavsen b WM H is Attmrney Patented 29,

man: I. mason, OI scmncrmr, m YORK, moron T PATENT orrlcs.

ennui MC COIPAIY, A COB-YORATIOI OF mzw YORK.

nmzcsmr mrumox.

Applloutlon ma l'ellmry 10, mo. Serial In. sum.

To'aZZ whom it may. concern:

Be it known that I, Enxsr F. W. ALEX- sncnnsoie, a. citizen of the United States, residing at Schenectad county of Sche- 5 nectady, State of New ork, have invented certain new and useful Improvements in Electric Ship Propulsion, of which the following is a specification.

lily invention relates to electric propul- 16 sion and more particularly to electricship propulsion.

An object of my invention is to rovide a system of electric propulsion whic will be. reliable and elficient in operation and which will extend the advantages of electric proulsion to low speed boats such as cargo ate and the like.

A further object of my invention is to provide a svstem of. electric ship propel 96 sion particularly adapted for use with propeller driving motors adapted. to operate as synchronous motors.

, A. further object of my invention is to provide methods of operating electric ship '33 propulsi equipments which shall facilitote the use of propeller driving motors of the synchronous ty and which shall make it possible, with suc motors, to develop, sine ply and reliably the high torque necessary:

or maneuvering purposes.

A further object of my invention is to provide control mechanism and connections which will facilitate the operation of ship propulsion systems, enabling dillicult maneuvering operations to be carried out without the exercise of a high degree of skill on the part of the operator. j ,My invention will be better undelstood from the following description taken in connection with the accompanving drawings, and its scope will be pointed out in the appended claims.

' The r A1 is.

uncmeuts that mustbe met in electric ship propulsion equipmentsof generel utility are unfavorable to induction motor design because of the low propeller speeds encountered. Considerations of emmen and economy usually require it high 5 turbine driven generator, and even .t ough a bipolar generator be used, the in.- quenc of the generator output will freuent y require a propeller motor mm 60 to 80 poles. An induction. motor have a very low power factor or a dangerbmke on' the propeller. In order to make designed to meet the conditions imposed will ously small air gap, whereas the synchronous motor can be not only lighter but better in these respects. Difilculties lie in the way of using propeller driving motors of the synchronous type, however, for the reason that the synchronous motor characteristics are such that its starting and reversing torques are relatively small, even when the motor is provided with some. well known form of squirrel cage windin L The requirements that a ship p'ropu sion motor must fulfill, in order to be adapted to the characteristics of the propeller during the various maneuvering operations, have been determined experimentally. The results indicate that the momentum of the ship dragging the propeller through the water causes the propelier to be driven with considerable power by the water as a turbine, and that it cannot be stop d unless a torque nearly equal tothe full loa torque o'fthe motor is exerted to breakthe propeller away from the water. This maximum tor ue occurs at a speed of about 35 r cent. liter this point-has been passed, t e propeller can easil be stopped, and can be held at stand-stil by brakin torque of only 40 per cent of the full-loa( torque. If aquick stoppin of the ship is to be 'efieeted, it is not on y necessary to stop the propeller, but it must be revolved in the opposite direction. Full-load motor torque in the reversed direction is required to revolve the propeller at 33 per cent speed backwards. In order to design a. motor to meet the requirements for quick maneuver ing and reversal of the propeller, it is ob-, viously necessary to have a motor, which can not only deliver a considerable driving torque to thepropeller when it rotates in the reversed direction, but which also has a braking effect as high as full-load driving torque in order t'o-stop the propeller before it can be reversed.

Amer-ding to my invention I use a propeller driving motor having synchronous motor characteristiw and develop the torque necessary to break the pro r from the water and brin it approximately to standstill by using .c motor as an electric 10$ the propeller rotate in theopp'osite direc tion, I may proceed in a manner to take advantage of the peculiar characteristics of the combination of synchronous motor and synchronous generator which enable the motor and generator to stay together with continuity of torque characteristic from positive to negative rotation. According to this method of operation I am enabled to avoid the use of external rheostats or their equivalent in the form of high resistance windings and am enabled greatly to simplify the process of reversing the ship. My invention is not limited, however, to such method of reversing the propeller rotation, since it also includes the idea of securing such reversal, after the propeller has been substantially stopped, by operating the motor as an induction motor. According to this modification of the system and method of operation, the propeller driving motor is first operated as a synchronous generator to break the propeller from the water and bring it ap proximately to stand-still, then operated as an induction motor to reverse the propeller and bring it substantially to synchronism in the reversed direction, at which time synchronous operation is restored.

Referring to the accompanying drawings, Fig. 1 is a diagrammatic representation of a ship propulsion system comprising a turbine driven s chronous generator and a propeller driving motor of the synchronous type arranged for propeller reversal by synchronous motor action; Fig. 1 is a sequence chart showing the preferred method of operating the system shown in Fig. 1; Fig. 2 is a diagrammatic representation of a modified form of ship propulsion system in which means are provided for holding the propeller at stand still by short-circuiting (onnections; Fig. 2 is a sequence chart correspondingto Fig. 2 Fig. 3 shows a modified form of ship propulsion system arranged for propeller reversal by induction motor action; Fig. 3 is a sequence chart corresponding to Fig. 3; Fig. 4 shows a modified arrangement of circuit connections for performing the same operations as are performed in Fig. 3, the circuit connections being arranged for controller operation; Fig. 5 is a diagrammatic re resentation of a system comprising contro ler operated circuits for performing the operations of synchronous braking, induction motor reversal and synchronizing, together with relays insuring the proper operation of the various connecting devices; Fig. 6 is a diagrammatic representation of an entirely automatic system including means dependent upon the direction of propeller rotation for controlling the circuit connections; Fig. 7 is a diagrammatic representation of a modified arrangement of excitation circuits showing interlocking mechanism between the controller and steam levers; Figs. 8 and 9 are details showing the operation of the sthp for the steam lever; Fig. 10 is a diagrammatic representation of a system comprising two propeller driving motors supplied from a single generator with connections, whereby the motors may be interconnected for electric braking; Fig. 11 shows a modified form of system in which a plurality of generators and motors are used; Fig. 12 shows a system in which a plurality of motors are supplied from independent windings on the generator; Fig. 13 shows a modified form of ship propulsion system in which the idea of single phase braking is involved; and Figs. 14 and 15 represent a synchronous motor provided with double squirrel cage windings of a type particularly adapted for use in certain of the modifications of my invention.

Referring to Fig, 1, an elastic fluid turbine 1 is arranged to drive directly the revolving field member 2 of a synchronous generator whose stator 3 is adapted. to be connected to the stator 4 of a propeller driving motor whose rotor 5 is directly connected to the propeller 6. Circuit controlling and reversing contactors 7, 8, 9, 10 and 11 are provided in the connections between the stator windings 3 and 4. With contactors 7, 8 and 10 closed, the phase rotation is such that the propeller is driven in one direction, and with contactors 7, 9 and 11 closed, the phase rotation is reversed to reverse the direction of propeller rotation. The-propeller motor rotor is represented as a bipolar salient pole revolving field structure provided with. an exciting winding 12 connected to slip rings 13 and 14. The rotor is provided with a squirrel cage winding 15 to enable the direction of rotation to be more An exciter16 is arranged to supply current in series to the exciting winding 12 of the motor and the exciting winding of the revolving field member 2 of the generator, which winding is connected to slip rings 17 and 18. An adjustable resistance 19 is shown in parallel with the field winding of the generator to indicate that the excitation current in the motor and generator field windings may be adjusted to independent values if desired. The exciter 16 is represented as provided with a fieldwinding 16' excited from any convenient direct current source. Any suitable means for adjusting the field strength of the exciter is indicated by the adjustableresistance 19'. A switch 20 indicates a suitable means for interrupting the exciter field circuit to deenergize the field windings of the motor and generator. The turbine is represented as providedwith a speed governing mechanism 21 for automatically maintaining any approximate speed which may be desired, whether the turbine is loaded or unloaded. A speed admenses justing lever 22 is provided whereby the governing mechanism may be adjusted to old any desired speed. This lever is intended to be arranged, in the modification shown in Fig. 1, to reduce the steam admission substantially to nothing when desired. The governin mechanism indicated in the drawin is of t e type re resented in the United btates patent to mmet, No. 1,137,308, dated April 27, 1915. It is to be understood, however, that my invention is not limited in any respect to any particular construction or type of overning mechanism for the turbine. llfliatever type of governor is selected must be desi ed to mid the turbine at a very iow spee but as heretofore indicated, it is immaterial as far as my invention is concerned whether a centrifugal governor, a continuous flow geared oil pump type governor, or some other type of vernor is used. I he operation of the modification shown in Fig. 1 will be readil understood from a description of the met ods which I have devised for stopping and reversing the propeller. if it be assumed that the ship is proceeding at full speed ahead, the contactors 7, 8 and 10 Will be closed. The exciter field switch 20 will be closed and the exciter 16 will be supplyin current in series to the field, windin 2 and 12 of the generator and motor. ormal excitation will thus be supplied to both generator and motor. The steam lever 22 will be opened to whatever positionmay be necessary to hold the desired speed, which position will depend upon the navigating conditions obtaining at the time. This phase of operation is indicated in Fi 1 h the legend FULL SPEED AHEA If it be now desired toreverse the ship the fieldcircuits of generator and motor will first be deenergized, as for example, by opening exciter' switch 20, lever 22 will be moved until the steam admission to the turbine is entirely shut oii. Switches 7, Sand 10 will be opened.

driven by the inertia of the moving parts of the generator and turbine, and the eld ole-.- ment 5 of the motor is driven the propeller 6 which is being dra ged' through the water by the momentum o the ship. The

result is, therefore, that we have twogenera -l tors short circuited upon each other with reversed phase rotation. A powerful synchronous braking torque is thus exerted upon the propeller 6 to break it away from the water and bring it to standstill. The braking energy developed in the motor is dissipated-largely in the solid field cores of the generator rotating field element 2 by the eddy-currents therein developed. In addition to this energy dissipation, energy is dissipated in the motor and generator windings. An additional braking torque is superposed upon the synchronous braking torque by the induction motor action of the generator upon the squirrel cage winding 15 of the motor. It is obvious that the in terchange current between the two machines prcces torque reactions which rapidly slow the two machines down approximately to standstill. The two machines will get into step automatically and the operator may start the reverse operation at his leisure by moving the lever 22 to put steam on the turbine again. I thus take advantage of the peculiar characteristics of the combination of synchronous motor and synchronous generator which enable the continuity of torque characteristic to be maintained from positive to negative rotation even though the turbine be brought to standstill during the opera tion.

The description of operation given in connection with the maneuvering operation which involves changing from full 5 eed ahead to full speed astern is believe to make perfectly clear how other maneuvering operations. are performed. It is apparcut that acceleration of the ship from stand still will be accomplished by first, manipulating the contactor switches for the desired direction of operation, after which excitation will be applied to both motor and generator and steam gradually admitted to brin the machines up to speed synchronous y. Similarl if, vwhen the ship is.

drifting ahead it desired to accelerate to full speed ahead the turbine will be brought to a speed such that the generator and motor will be in substantial synchronism before the exciter switch 20 is closed. If, on the other hand, while the ship is drifting ahead, it be desired to reverse the motion of the ship the operation of synchronous braking will precede the operation of synchronous reversal.

In the arrangement heretofore described,

the steam required to beadmitted while the turbine is at ornear standstill may involve:

such temperature changes as are in urious to steam turbines as at This objection may be iminated to a great extent by the arrangement shown in Fig. 2.

In 'this arrangement, the generator is ar ranged to be connected to-supplycurrentto the propeller driving motor as' in Fig. I,

resent constructed.

and the turbine is provided with a speed adjusting lever 22 as in Fig. 1. -The arrangement' differs from the arrangement shown in Fig. 1 by the provision of means for holding the motor at standstill by a short circuit across its terminals which is put on after the motor is stopped. This short circuiting means comprises normally open contactors 23 arranged to be closed by coils 24 arranged to be supplied from any convenient source, represented in the drawin as the source of excitation for the exciter eld winding 16'. A switch 25 is provided in the circuit leadin to coils 24. Switch 25 is arranged to be closed automatically when the propeller motor is at standstill. Contacts 26 are also provided in the circuit of coils 24 and these contacts are arranged to be closed when the lever 22 is in position to shut steam off from the turbine.

The operation of the modification shown in Fig. 2 in the maneuvering operation which consists in reversing the direction of the ship from full speed ahead to full speed astern is identical with the operation set forth in connection with Fig. 1 up to the point where the propeller reaches standstill. At this phase of the operation switch 25 is closed, and inasmuch as the steam lever 22 is in closed position at this phase of the operation, the circuit of coils 24 is closed at contacts 26, and the contactors 23 are, therefore,

closed to establish ashort circuit across the motor terminals. This short circuit holds the propeller motor at standstill and the operator can wait, without heating the turbine, until the ship has reached a speed at which reversal will take lace as soon as he opens the steam lever. Ks soon as this speed has been reached, the operator will move the lever 22 to readmit steam to the turbine to efiect synchronous reversal of the propeller in the manner set forth in connection with Fig. 1. The movement of the steam lever 22 at once interrupts the circuit of coils 24 to release the contactors 23, which interrupt the short circuit across the motor terminals. It will be observed that the switch 25 and contacts 26 are interlocked in such a way that the short circuit for holding the propeller at standstill will be established only when the motor is at standstill and the steam is off. It will also be apparent that the contactors 23 may be operated in the mannerdescribed without excessive arcing, even though the generator and motor the generator speed is very low when the short circuit is made and broken.

' The feature of synchronous reversal and the idea of means for holding the propeller at a standstill are claimed in my divisional application Serial No. 500,024, filed September 12, 1921, for electric ship propulsion, assigned to the assignee of th1s application.

field, circuits remain closed, for the reason that In the modifications shown in Figs. 1 and 2, I have shown the exciter connected to supply the generator and motor field windings 1n series, but it will be apparent that my Invention is not limited to any particular arrangement of connections for the exei tion,-and the connections between the generator and motor stators 3 and 4, are identical wlth the corresponding features shown 1n Fig. 1. The turbine governing and speed mechanism is also identical with that of Fig.

1. The exciter 16 is, however, connected so that it can not only supply the generator and motor field windings in series, but also, so that its full capacity and voltage may be applied to either field winding separately, whereby over-excitation may be produced on either the generator or the motor. In this modification of my invention I prefer to use an exciter of considerably greater capacity than that necessary for normal operation, in order that, for a short interval of time, over-excitation may be simultaneously applied to both motor and generator field windings. A switch 27 is arranged to complete a circuit connecting the exciter 16 to supply the field windings 12 and 2 in series. A switch 28 is arran ed to connect the motor field winding 12 irectly across the terminals of the exciter 16. A resistor 29 is inafter described. A switch 30 is arranged to connect the exciter 16 directly across the.

terminals of the generator field Winding 2. A switch 31 is arranged to short circuit the resistor 29.

The operation of the arrangement shown in Fig. 3 is as follows:

During full s eed ahead contactors 7, 8 and 10 will be c osed and switch 27 will be closed to connect the generator and motor field windings inseries, as set forth in connection with the modification shown in Fig. 1, and this phase of o eration is indicated by the legend FULL FEED AHEAD in the sequence chart shown in Fig. 3". It now 'it be desired to reverse the ship the switch 27 is opened to deenergize the motor and generator field windings, after which the line contactors 7 8 and 10 are opened and contactors 7, .9 and 11 closed to reverse the phase rotation. During these operations the steam lever 22 will preferably have been moved to a position in which the speed of the turbine is reduced to about 25 per cent of its normal value. The switches 28-and 31 are now closed to apply the full voltage of the exciter to the motor field winding 12,

, applied to the motor while the generator field winding remains unexcited. A strong braking torque is, therefore, developed to break the propeller from the water and bring it approximately to standstill, the energy developed being dissipated in the genorator field structure and in the generator and motor windings, as set forth in conned tion with Fig. 1. When the propeller has been stopped, or nearly stopped, switch 80 is closed to apply over-excitation tothe genorator field winding. When the generator field current has had time to build 21:3,ll19

switches 31 and 28 are opened L3 disconnect motor field winding 12 from the excite!) 16. The system is now arrange-5. to function with strong induction motor torque to reverse the propeller, since the generator is over-excited and the motor wniding 12 deenergized. The reversing torque is produced in the squirrel cage winding 15 of the motor, As bereinafier indicated, a double squirrel cage winding may be used if desired. When the induction motor action brought the propeller substantially to synchronous speed in the reversed direction,

the switch is closed and the switch.

opened to connect the motor and generator field windings in series, which action brings the motor into exact synchronism with the generator, after which the lever adj 11sted to the ship to the desired speed in the reversed direction. The various operations performed in reversing the ship, which operations have just been described, are indicated in the se uence chart Fig. 3. In view oif the prece ing description the steps necessary for performing other maneuvering operations will be obvious.

Fig. shows a modified arrangement of excitation circuits in a system arranged to perform the operations of synchronous braking, induction motor revemal and. normal synchronous running, as in the modification shown in Fig. 3. In this modification I have shown a controller 32 arranged to con.-

trol the operation of the various switchesin the line and excitation circuits. It is obvious that a controller may be similarly arranged to control the circuits in the modifications heretofore described, but no such controller has been shown for the reason that I wish to emphasize the fact that my tor into exact syn The connections and operation of the modification shown in Fig. 4 will be most readil understood by considering the 0 ration o the system in paming from 111 speed ahead to full speed astern. With the controller segment 33 moved to FULL SPEED position, fingers (I, 0 and e of the controller will be energized, these contacts being connected by segment 33 to controller finger Z which is connected to any convenient source of power, Fingers a and 0 ma factors 7, 8 and 10 in closed finger c maintains switch 20 gize the field winding or Switches 35, 36 and 3'? are sition for the reason that coils are deenergized. The ez connected to energize field w 12 in series, Normal e "si plied to both generator and system operates synchron se-"Q, understood that in all arrang which the field windings are n series, means may be provi' pendently adjusting the generate tor field energization if desires that it is now desired quickly to rev c ship. The steam lever 22 will be moved, to the reduced speed or maneuvering pc tion and the controller 32 thro AHEAD to ASTERN position. controller goes through cit poor switches the system will drop out, troller segment 34 will then energize contact fingers c and (i to close contactors '7, to reverse the phase rotation between an tor and motor Controller se ment next energize contact fingers e switches and 35. The full cs acity of the exciter 16 will now be impressed upon the motor field win- 1mg '12 for the re s that the generator field winding 2 will short-circuited by the switch Strong synchronous braking torque will, therefore, be developed in the motor to bring it approximately to standstill. The controller segment 32 will then be moved to doenergize contact finger f and energize contact finger 9'. Switch 35 will, therefore, be opened and switch 36 closed immediately thereafter, The full voltage and capacity of the ex citer 16 will now be applied to the nerator fieldwinding 2, since the motor fie 61 Winding 12 will be short circuited by switch 36. Strong induction motor to ue is, therefore, exerted to reverse the prope er and accelerate it in the aster-n direct on. When steady conditions have been reached controller segment32 will be further moved to energize contact finger h to elm switch 37 and deenergize contact finger g to open switch 36. Resistance 38 is now connected in parallel with field winding 12 and this winding is energized to bring, the propeller driving mochronilm with the gener- Ill) , ing operated to change ill (ill

,ous operation in the ahead direction, s'egator. The controller segment 34 may now be operated to full speed positiondeenerizing fin er h to open switch 37 to connect eld windings 2 and 12 in series for normal synchronous operation. The controller diagram indicates that the-speed of the turbine is to be reduced while the controller is bethe connectionsto produce maneuvering operations. It will be understood, however, that after connections for normal synchronous operation have been established, the steam lever 22 may be adjusted to hold the ship at any desired speed.

' While the excitation circuit connections of lid Fig. 4 permit of a somewhat simpler method of operation than the connections of Fig. 3, it will be observed that the arrangement of Fig. 3 is preferable for the reason that the generator and motor excitation circuits may be independently controlled, while with the arrangement shown in Fig. 4, the excitation of one machine must be reduced when the exciting winding of the other is simultaneously energized.

The modification shown in Fig. 5 is arranged to provide the same excitation circuit connections as the arrangement shown in Fig. 3. The system is arranged for remote control by means of a controller 32 provided with segments 33 and 34 cooperatin with contact fingers a, b, c, d, z', j and 7c. The switches 27, 28', 30 and 31 and the resistance 29' correspond to the parts numbered 28 to 31 of Fig. 3. Relays are rovided for insuring that the transition irom synchronous braking to induction motor operation, and from induction motor operation to synchronous motor operation takes place only when conditions in the system are such as to determine the fact that the system may function properly when the changed connections are established. lnterlocks are also provided for certain of the switches for controlling the excitation circuits arranged to insure that proper time intervals are provided to enable the current in the generator and motor field windings to build up in order that the switching operations may be performed without danger of the generator and motor falling out of step. For normal synchronment 33' of the controller energizes contact fingers a and 0 to close contactors 7. 8 and as in Fig. 1. Finger i is energized to maintain switch closed to render the exciter active. Switch 27' is held closed in a manner hereinafter set forth, and the generator and motor field windings 2 and 12 are thereby connected in. series to the exciter 16 as in Fig. 3. Resistors 39 are provided 1n the connections between the generator and motor stator windings 3 and 4 to improve the power factor during synchronous braking. During normal synfrequency of S111) is induce chrononsoperation these resistors are short circuited 'by contactors 40,- the operating coils of which are energized from controller finger j. Normal synchronous operation, therefore, occurs precisely as in the modification shown in Fig. 3. \Vhile the governing and speed adjusting mechanism for the turbine is not illustrated in Fig. 5, it is to be understood that such mechanism is employed. The controller segments 33' and 34' are arranged to be moved by handle 41 and-a member 42 is arranged to more with the controller handle. Member 42 is provided with projections 43 to engage a pin 44 located so as to stop the controller in the position to establish braking connections, as hereinafter set forth. The member 42 is adapted to be moved to a position where the pin 44 will not be engaged, by a lever 45 provided on the controller handle. The member 42 may also be moved to disengaged position by coil 46. The member 42 is, however, normally held by the spring 47 in such position that the means 4-3 will engage the pin 44. A relay 48 is arranged to operate a contact 49 in circuit with coil 46. Rela 4-8 is provided with a winding 50 in the orm of a small direct current motor armature and this winding is supplied from any convenient source of direct current. The relay field winding 51 is arranged to be connected in one ofthe leads connecting the generator and motor stator windings I5 and 4. During synchronous braking, winding 51 is energized with alternating current. Relay 48 is provided with a pendulum comprising an adjustable weight 52 which maintains the contact 49 in open position when the winding 51 is unexcited. The relay is adjusted to have a natural period of one second. This relay will, therefore. remain open on a dead circuit and on high frequencies. but will close contact 49 intermittently on frequencies of about one cycle. A relay 53, similar in construction to relay 48, is arranged'to control a contact 54 provided fora purpose hereinafter set forth. Winding 55 of relay 53 is connected across the terminals of motor field winding 12 through sli rings 13 and 14. -A contact 28, interloc ed with contact 28', is provided in the'circuit of windin 55 for a purpose hereinafter described. ield winding 56 of relay 53 is arranged to be connected to any suitable direct current source. Relay 53 1s provided with an adjustable weight 57 arranged to hold the contact 54 normally in open osition. During induction motor operation a frequency corres onding to the in the motor field Winding 12, as will be obvious to those skilled in the art, and an alternating current having the. frequenc of slip is thus impressed 'upon the win ing 55 while the generator is supplying current to the motor iio . three cycles, but is arranged to remain open when direct current passes through the winding 55, which happens whenever the motor switch c ation o excite winding is excited and the opened, This condition of open ir when switch 2? is closed to enerator and motor field -Windles. Switch '2'? has mechanically therewith two interlock contacts Contact 27 is arranged in the w coil controlling switch 28 and contact arranged in circuit with the coil inng switch 30" Switch 30 1s interlock contacts 30* and a is arranged in the circuit oi the operating coil of switch 31''. The functi contact 30 will he hereinafter Contact 30 is arranged to have "eyed opening, the period of delay depend'ng upon the time constant of the mot 'r held winding 12. lontact 54L oi relay 53 is arranged to complete a circuit from nger ii: to coil 58 arranged: to close contacts 58 58* and 58 lontact 58 is arranged close a holding circuit for coil The function of contact 58 will be hereinafter set fortln Contact 58 is arranged control the circuit oi the operating col for switch 2'?" and this contact is arranged to have a delayed closing, the period c; delay depending upon the time constant oi the generator field winding 2. A switch 59 is arranged in parallel with contact enable the circuit of coil 58 to he closed manually whenever desired.

As is the case with the modifications here tot'ore described, the operation of the arrangement shown in Fig. 5 may be most readily developed by considering the maneuvering operation which consists in changing from full speed ahead to full speed astern. The connections established when controller se ment 33 is moved to the FULL SPEED ATIEAD position have been set forth in the preceeding description of this modification. As the controller 1s moved through oil-position all of the switches and contactors fall out deenergizing all circuits. The controller segment 34 energizes controller fingers c and dto close contactols 7, 9 and 11 for reversed phase rotation. Controller finger i is next energized to close switch to render the exciter 16 active. Pin 44 engages projection 43 of member 42 to stop the controller in thisposition, which is the braking posis tion, as will be evident from the fact that :ontroller finger i completes a circuit through interlocks and 27 to the oper-' ating coil of switch 28'. Switch 28', therefore, closes to throw the full capacity of exciter 16 upon the field winding of the motor for strong synchronous braking. A circuit is also completed from controller finger 2 through interlock contact 30 to clos switch 31' and short circuit the resistance 29. The oi-airing currents circulating in the connections between stator windings 3 and i are arranged in this modification to traverse resistors These resistors are shown for the purpose of indicating how the power factor of braking circuit may be proved desired. The circulating braking currents obviously decrease in frequency as propeller sloWS down and the frequency coil 51 correspondingly decreases. its heretofore set forth, the construction of relay is such that the contact 49 remains open until the frequency of the braking currents is reduced to about one cycle per secend. When this low frequency is reached the propeller will have been brought approximately to standstill and the contact 49 closes a circuit from controller finger c to coil to move member 42, so that pin 44: no longer prevents movement of the controller handle 41. Further movement of controller segment 34 energizes controller finger j to efiablish a circuit for the peratcoils of contactors 40, which thereupon short circuit resistors 39. One of these contactors also short circuits the coil 51 of the relay 48 which thereupon ceases its intermittent operation and contact 49 remains open as heretofore described. Controller finger j also completes a circuit through interlocl; contact 27 to the operating coil or switch 30. Switch 30', therefore, closes and app-lies the full voltage of the exciter 16 to the field winding 2 of the generator. At this instant over-excitation is supplied both to the motor and generator field windin 5, thus throwing an excessive load on exciter 16. This load is of short duration, however, for the reason that interlock contact 30 opens after an interval long enough to permit the current in the generator field winding to rise to full value, and the openingof contact 30 causes switch 28' to open and deen ergize the motor field winding 12, By thus delaying the change in the circuit of motor field winding 12 until after the generator field Winding 2 has built up, I avoid the danger of the propeller slipping away during the time that it takes the current to build up in the generator field winding. It is obvious, however, that my invention is not limited to any particular way of securing this time interval between changes in the field circuit connections, since my invention covers broadly the idea of roviding a means for performing this function in the combination, and it is immaterial whether the degenerator field current or by the more practical means herein disclosed. From the pre ceding description, it is now obvious that the strongly excited generator supplies current to drive the propeller motor as an induction motor" with strong reversing and accelerating torque. When switch 28 opened, interlock contact 28 closed the circuit of winding of relay 53. Winding 55 is, therefore, now subjected to the frequency induced in the motor field winding 12 by the currents circulating in the stator winding 4. As heretofore indicated. this frequency corre sponds to the frequency of slip of the propeller driving motor which is now operating as an induction motor. As heretofore indicated, contact 54 of relay 53 remains open until the frequenc of slip falls to about three cycles at whlch time this contact begins to close intermittently. If the controller has been moved to the FULL SPEED ASTERN position, the first closure of contact 5t completesv a circuit from controller finger it" to coil 58 w hich is arran *ed to operate contacts 58 58 and 58. 'ontacts 58 and 58 close inunediately, the former completing a holding circuit independent of contact 54-, for coil 58. Contact '58 completes a circuit through interlock contact 27* to close switch 28. The closure of switch 28 energizes field winding 12 ofthe motor to bring it into synchronismwith the generator. After an. interval of time sufficient for the motor field current to be established, contact 58 closes to energize the closing coil of switch 27'. At the instant switch 27 closes, interlock contact 27 opens switch 28 and interlock contact 27 opens switch 30. During a small interval of time switches 27, 28' and 30 are closed and the resistance 29' is, therefore, provided for the purpose of preventing a short circuit on the exciter 16, which circuit would lead from one terminal of the exciter through switches 30', 27' and 28' to the other terminal of the exciter. Normal synchronous operating conmotions are now established for operation in the astern direction, thefield windings 2 and 12 being connected in series through switch 27'.

The function of contact 28 in the circuit of winding 55 of relay 53 of Fig. 5, will now bedescribed. If winding 55 were connected directly to the terminals of field winding 12, and the relay arranged to hold contact 54 open with a direct electromotive force appliedto its terminals, it is apparent that a kick would be produced tendin to close the contact whenever the circuit of old winding 12 is interrupted. 'With such an arrangement, upon the opening of switch 28 at the completionof synchronous braking, contact 54 would energize coil 58, which would'thereafter be held closed by contact 58*. Contact 58 would immediately reclose switch 28 to restore-the direct current excitation to the motor field winding, although the slip would be high and the motor so near standstill that it could not get into step with the generator. A moment later the contact 58 would close switch 27' andopen switches 28' and 30., establishing a circuit "connecting the two field windings in series for normal synchronous operation, although it would be impossible for the motor to get into step with the generator. To

prevent this undesirable operation, contact 28 isarranged to complete the circuit of winding 55 only while switch'28' is in the open position. Winding 55 does not, therefore, experience the kick due to opening the motor field circuit at switch 28.

While I have described the relays48 and 53 as adjusted to effect the closing of their contacts at frequencies of one cycle and three cycles per second respectively, it is obvious that my invention is not limited to any particular frequency of operation. llt is merely essential that contact be made only when the condition of the-system determines that the system may function properly after the transition is made from one phase of operation to'the next. lt is, moreover, apparent that my invention is not limited to the particular means disclosed for controlling the transition from one phase of operation to the next, since frequency responsive relays of other types may be substituted. It is further apparent that my invention is not even limited to frequency responsive devices of any charactor for controlling the transition operations, since broadly considered, my invention contemplatesthe provision of means responsive to any condition which will determine that the system will operate properly with the changed connections which are to be established.

The mechanism for normally stopping the controller in the. braking position is provided to insure against the operator of the system involuntarily performing a maneuvering operation which requires synchronous braking without pausing on the braking position of the controller. It is apparent, however, that for certain maneuvering operations synchronous braking is not necessa .or desired. If, for example the ship be d rifting ahead and it be desired to chan e to full-speed-ahead, it is obviously not desirable to go through the synchronous braking phase of operation which would first bring the ship to a standstill. In order to enable this operation to be performed withoutsynchronous braking, the lever 45 is provided. By gripping I this lever with the controller handle, e operator may pass through the braking position without pausmote control.

ing long enough to establish braking con-I nections.- It is apparent that my invention is not limited to any particular means for performing the function of eliminating the synchronous braking phase of operation.

It is apparent that synchronous braking is desired whenever the ship is to be brought quickly to a stop, even though it be not desired to move astern. Such quick stopping will be performed by throwing the controller to reverse position for synchronous braking and then to off position exactly as the corresponding operations are performed for ship propulsion systems operated by steam engines. This method of operation is, of course, contemplated in all of the modifications hereinbefore described.

Fig. 6 represents an entirely automatic ship propulsion system arranged for re- All maneuvering operations may be performed by mere manipulation of the. controller I to accomplish the desired maneuvering; synchronous braking, induction motor reversal, and synchronizing be-- in}; automatically performed when necessary and at the proper time. The various connections established and the relays are practically the same as in the arrangement shown in Fig. 5, the rincipal difl'erence being that a direction re ay'60 is provided for eliminating the operation of synchronous braking when it is unnecessary and undesirable. The direction relay comprises a disc 61 on the motor shaft arranged to operate the pivoted lever 62 in one direction or another according to its direction of rotation. v The lever 62 is arranged to operate contacts 63 and '64 which are arranged to complete circuits leading from controller fin rs 0 and Z respectively. Asshown in t a drawing, the

disc 61 is arranged to rotate counterclockwise when the pro ller.is running forwards and to run c ockwise when the propeller is running backwards. Forward rotation closes contact 63 and backward rotation closes contact 64. Relay 48 difi'ersfromrelay 48 of Fig. 5'in that the contact 49' is arranged to be normallyclosed instead of normally opened. This is accomplished by arranging coil in series with coil 51 and arranging-this coil so as to tend tc-hold the contact 49 open. Thearrangement is such that with frequencies above those at which it is safe to change the connections from synchronous braking to induction motor operation, the contact 49' will be held open. At thepredete'rminod frequency contact 49' closes.

' The operation ofthe arrangement shown in Fig. 6 is as follows:

' During full-speed-ahead the controller segment 33- maintains switches 7, 8 and 10 closed as in the modification shown in Fig. 5. The contact 63 of the direction relay will be closed. The switch 27' will be in (Blond pothrow the controller to sition to excite the motor and generator field windings in series, as in Fig. 2. To reverse the ship, it is merel necessar to throw the controller from F LL SP JED AHEAD position to FULL SPEED ASTER-N osition. As the controller goes through 0 osition, the line contactors and excitatlon controllin' switches drop out, as in Fig. 5. The ASTFRN segment 34" first energizes controller fingers c and d to close contactors 7, 9 and 11 for reversed phase rotation. No circuit is completed at controller finger Z for the reason that contact 64 is open. Controller finger m is energized to close switches 20, 28' and 31, as in Fig. 5. Over-excitation is thus applied to the motor for synchronous braking. quency of the braking currents falls to the predetermined value, relay 48 closes contact 49' and completes a circuit from con- When the fretroller finger n to close contactors 40 to short circuit resistors 39. One of the contactors 40 is provided with an interlock contact 40 which completes a circuit from controller finger m through interlock contact 27 to the operating coil of switch 30'. Switch 30', therefore, closes and applies over-excitation to the generator field winding 2. Switch 31' opens; immediately and switch 28 opens after the interval determined by contact 30", i

as in Fig. 5. Theopening of switch 28' deenergizes the motor field and interlock 28 connects winding 5530f relay 53 across the terminals of the excitier field winding, as in Fig. 5. Induction motor reversal of the propeller now takes place and upon this reversal the direction rela and opens contact 63. on'taet 64 is, however, at this time in parallel with contact 49', which is closed, and the closi of contact 64, therefore, has no effect. e opening of contact 63 has no effect for the reason that controller finger o is unener 'zed at this time. When the slip of the motor as been reduced to the predetermined value, relay 53 closes closes contact 64 contact 54 to establish synchronous motor operation connections exactly as in 5.

To explain the operation of the direction relay, assume now that,vwhile the ship is movin full-speed astern, that the controller be thrown to OFF position permittin the ship to drift astern. -While the ship is riftin assume that it be desired to change to in L-speed astern. The operator will merely STERN position. lontroller fingers 0 and (i will close. contactors 7, 9 and 11 for astern operation, and controller finger Z will com lets a circuit through contact 64 of the irection relay, which is now closed, directly to the operating coils of contactors 40. It will be observed that this circuit shunts the contact 49' of the relay 48', andthat connections III are, therefore, at once established, which contact 49' closed. Interlock contact is, therefore, at once closed to close switch 30 for induction motor operation, and the operation of s nchronous braking is thus eliminated. It is believed that other maneuveriing operations will be obvious from the maneuvering operations described.

Th combination of a ship propulsion system involving a direction relay or its equivalent for eliminating synchronous braking is claimed in the application of D. C. Prince, Serial No. 365,762, filed March 15, 1920, assigned to the assignee of this application.

It will be understood that governing and speed adjusting means are provided for the turbine 1 of the arrangement shown in Fig. 6, as in the modifications heretofore described.

In the modifications heretofore described, it have represented the exciter as arranged to supply normal excitation to the generator and motor field windings in series and in certain modifications I have represented connections whereby overexcitation may be applied to said field windings. The modification shown in Fig. 7 involves the use of a three-wire system for exciting the field windings and such a system is particularly well adapted for carrying out my methods of operation for the reason that the field windings maybe readily excited either independ-' ently or together with normal or double voltage. Fig. 7 represents a system in which the operation is arranged for remote control by means of a controller 60 operated by a lever 61'- The governing mechanism 21 of til the turbine is arranged to be controlled by a steam lever 59 which is interlocked with the control lever 61 as hereinafter described. The conventional showing of the controller segments indicates that all of the segments on the ahead and astern sides of the controller are electrically connected together. The mains of the three-wire system are re resented by the lines 62', 63' and er, t e

neutral 63 of which is indicated as rounded to complete the circuits'supplying thewindings for operating the various switches. A switch 68 is arranged to connect the motor field winding 12 across lines 62' and 64: for overexcit-ation. A switch 69 is arranged to short circuit an adjustable resistance 65. A switch 70 is arranged to connect the motor field winding 12 across mains 62' and 63' for normal excitation, and resistance is provided for the purposes of adjusting this excitation to any desired value to control the power factor of the motor. A switch 71 is arranged to connect the generator field winding 2 across the mains 63 and 6 1 for normal excitation of the generator, and switch 72 is arranged to connect the generator'lield winding across mains 62' and 64: for over-excitation. A switch 73 is provided enabling the transition to be made from.

over-excitation to normal excitation on the generator without short circuiting one side of the three-wire system. The switches 68, 70, 71 and 72 are provided with certain interlock contacts, the function of which will be set forth in connection with the description of the operation. The electric controller lever 61 and the steam lever 59, as hereofore indicated, are interlocked in a manner to insure that the turbine speed shall be reduced during maneuvering to enable the generator and motor to get into step more readily. The steam lever 59 is provided with a cam member 74; cooperatin with a pivoted locking member 75 provided with a roller 76 bearing on the cam surface. The electric controller lever 61 is provided with a member 77 provided with a plurality of notches in which the looking member 75 is arranged to engage. I have shown the member 77 as provided with three notches corresponding to the OFF, FULL SPEED AHE D and FULL SPEED ASTERN positions of the electric controller. The cam surface of the member 7 4 is so arranged that the steam lever 59' must be moved approximately to the 25% speed position before the control lever 61 can be moved. It is also apparent that the parts cooperate to prevent mani ulation of the steam lever 59 unless the e ectric control lever is in one of its three specified positions. A pivoted stop mechanism 78 having a projection 79 is arranged normally to stop the steam lever in the best maneuvering position, and this osition may sired to run the equipment at a very low speed in order to keep head-way or sternway in case of a storm or for standby purposes, the latch 7 8 maybe thrown to render the stop 79 ineffective and permit further movement of the lever 59 as shown in Fig. 9. The additional movement may be limited in any desired manner, but, as shown, the final stop is produced by the engagement of the lever 59 with the curved surface 80 of the member 78. As soon as the steam lever 59 is moved to increase the speed, stop member 78 falls back into place locating the steam lever in the maneuvering position when it is again moved to reduce the turbine speed. By this arrangement of levers and stop mechanism, the control is rendered more certain and the skill re uired on the part of the operator is reduce This stop mechanism arrangement is claimed in my the 

